Digital Mold Texturizing Methods, Materials, and Substrates

ABSTRACT

Methods, materials, and systems for texturizing mold surfaces is disclosed. In one method and system of the invention, a first step involves generating a graphics file of a desired texture pattern. The graphics file is subsequently output to an ink jet printer, which is configured to print using an acid-etch resist ink. The acid-etch resist ink is formulated to provide optimal properties for ink-jet printing, while also providing excellent acid-etch resist and superior handling properties. The acid-etch resist ink is printed onto a sheet of a carrier substrate that allows the acid-etch resist to be transferred to a mold surface, after which the mold surface is etched with a strong acid.

PRIORITY

The present application claims priority to U.S. Provisional ApplicationSer. No. 60/760,208, filed Jan. 19, 2006 (entitled “Digital MoldTexturizing Methods and Materials”), and U.S. Provisional ApplicationSer. No. 60/884,115, filed on Jan. 9, 2007 (entitled “Digital MoldTexturizing Methods, Materials, and Substrates”).

FIELD OF THE INVENTION

The present invention is directed to a method and materials fortexturizing molds. In particular, the invention is directed to a methodof texturizing molds using ink jet printing of an acid-etch resist ontoa transfer substrate, and then transferring the acid-etch resist to amold surface to be texturized.

BACKGROND

Currently, patterns for texturizing molds are typically prepared bymethods that are either inefficient, produce inferior results, or arelabor intensive. For example, current methods include a rice paperprocess that deposits a wax-based acid-etch resist onto rice paper. Thisrice paper method involves making acid-etched zinc plates as a primarymeans of generating texturing patterns. The wax is pressed into the zincplates, transferred to the rice paper, and then applied to a moldsurface using the rice paper. This method is expensive andtime-consuming. A further problem is that the rice paper is nottransparent, making placement of the patterns more difficult,particularly when registration with adjacent patterns is desired. Inaddition, the wax-based acid-etch resist can soften during application,causing a deterioration and distortion of the pattern, thereby producinga lower-quality mold.

An alternative method utilizes screen printing of a pattern onto carriersubstrate, and then transferring the pattern to a mold substrate to beetched. This method is popular for some applications, but is relativelyexpensive, and the patterns often fail to meet specifications due to thefact that the graphics files are screen printed. It can be particularlydifficult to create highly precise patterns using screen printedpatterns. Also, using this method it is difficult to produce preciselyregistered images, which are needed to texturize molds with multipledepths of etch.

Therefore, a need exists for improved methods of making a texturedpattern on mold surfaces.

SUMMARY OF THE INVENTION

The present invention is directed to methods, materials, and systems fortexturizing mold surfaces. In one method and system of the invention, afirst step involves generating a graphics file of a desired texturepattern. Typically such graphics files are generated on a computer. Thegraphics file is subsequently output to an ink jet printer, which isconfigured to print using an acid-etch resist ink. The acid-etch resistink is formulated to provide optimal properties for ink-jet printing,while also providing excellent acid-etch resist and superior handlingproperties. The acid-etch resist ink is printed onto a sheet of acarrier transfer substrate that allows the acid-etch resist to betransferred to a mold surface, after which the mold surface is etchedwith a strong acid.

Suitable acid-etch resists printed using the ink jet methodology includewater based and solvent based compositions. Various phase-changematerials, such as thermally or UV curable compositions, can be used.After printing and curing (by UV curing or solvent evaporation, forexample) the resist should demonstrate adhesion to high carbon steelwhile being acid resistant to strong acids such as nitric acid andferric chloride. The acid-etch resist should also typically withstandthe operating temperatures associated with ink jet print heads.

The carrier transfer substrate onto which the acid-etch resist isdeposited can contain one or more layers. For example, it can contain aremovable carrier layer (such as polyester) with a release coating, orcan contain a removable carrier layer with an additional binder layerand/or ink receptive layer. Thus, in some embodiments the carriersubstrate contains an insoluble carrier layer and an ink receptive layerthat is removable from this carrier layer. The ink receptive layer maybe adhered to the insoluble carrier layer by the binder layer. In suchembodiments, after the acid-etch resist is printed onto the inkreceptive layer, the insoluble carrier layer and binder layer are peeledapart and the carrier layer discarded. The binder layer and inkreceptive layer, which has an acid-etch resist pattern printed onto it,are then applied to a metal surface to be etched. Pressure is applied tothe exposed surface of the binder layer so as to press the ink jetprinted pattern of acid-etch resist onto the metal surface to betexturized. Thereafter the binder layer can be removed, such as byoxidizing, moistening, heating or further exposing to UV radiation. Theacid-etch resistant pattern remains attached to the surface to betexturized after removal of the binder layer, and the texturizationprocess can proceed by exposing the metal surface to an acid.

Advantages of methods of the invention over prior methods include thatthe methods of the invention are a digitized process that does not usescreen printing, allow for accurate reproduction of images with preciseregistration, and permits an ease of pattern production without chemicaletching of a zinc plate. Also, the methods can use customized patternsmade on-site with no need to send pattern files to outside serviceproviders, thereby promoting considerable ease, speed, and reliabilityof the process. Finally, the methods do not involve photolithography andcan be done at very high quality.

The above summary of the present invention is not intended to describeeach disclosed embodiment of the present invention. This is the purposeof the detailed description that follows.

FIGURES

The invention will be more fully explained with reference to thefollowing drawings, in which:

FIG. 1 shows a cross section of a carrier substrate suitable for usewith the invention, prior to deposition of an acid-etch resist.

FIG. 2 shows a cross section of a carrier substrate after deposition ofan acid-etch resist.

FIG. 3 shows a cross section of a carrier substrate after deposition ofan acid-etch resist and after application to a metal surfacesubstrate.

FIG. 4 shows a cross section of the acid-etch resist after applicationto a metal surface and after removal of the carrier substrate, butbefore acid etching.

FIG. 5 shows the metal surface after etching but before removal of theremaining acid-etch resist.

FIG. 6 shows the metal surface after etching and after removal of theremaining acid-etch resist.

FIG. 7 shows a photograph of an acid-etch resist deposited onto appliedto a carrier substrate, the acid-etch resist having undergone initialcure to anchortack the resist to the substrate.

FIG. 8 shows a photograph of a metal surface etched using the acid-etchresist of FIG. 7.

FIG. 9 shows a photograph of an acid-etch resist deposited onto appliedto a carrier substrate, the acid-etch resist having not undergoneinitial cure to anchortack the resist to the substrate.

While principles of the invention are amenable to various modificationsand alternative forms, specifics thereof have been shown by way ofexample in the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the invention tothe particular embodiments described. On the contrary, the intention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the disclosure.

DETAILED DESCRIPTION

The present invention is directed to methods, materials, and systems fortexturizing mold surfaces. As described below, the materials include anink jetable acid-etch resist that is printed onto a carrier substrate.The carrier substrate allows the acid-etch resist to be temporarilyretained, but the resist is thereafter transferred to a metal moldsurface that is to be etched.

Acid-Etch Resist

The acid-etch resist can include a liquid that is printed by ink jetusing drop-on-demand (DOD) print heads. Suitable acid-etch resistsprinted using the ink jet methodology include those that are water orsolvent based compositions. After printing and curing (such as by UVcuring or solvent evaporation) the resist should demonstrate adhesion tohigh carbon steel while being acid resistant to strong acids such asnitric acid and ferric chloride. The acid-etch resist should alsotypically withstand the high operating temperatures associated with DODprint heads (up to 90° C., and be transferable from the carriersubstrate to the metal surface).

In certain embodiments, for example, the acid-etch resist can includewater and acetates. The acid-etch resist can also include varioussolvent based dilutable pressure sensitive adhesives (PSAs). Theprintable composition acid-etch resist can include various solvents,including alcohols having more than four carbons, glycols, polyols,glycol ethers, glycol ether esters, ketones with five or more carbons(including cyclic ketones), hydrocarbons (alkanes, aromatics,cycloaliphatics), lactates (greater than butyl-), and esters (greaterthan butyl acetate).

As noted above, the acid-etch resist should be printable using an inkjet printer. The parameters of the printable acid-etch resist todetermine ink jet-ability include, for example for some embodiments,having a viscosity of 8 to 20 cps at a temperature range of 20 to 90° C.It is important to select a viscosity that: allows the acid-etch resistto flow properly prior to ink jetting, allows the acid-etch resist to beadequately jetted out of the ink-jet apparatus, and still allows theacid-etch resist to form a compact deposit onto the carrier substratethat does not readily flow laterally so as to blur the depositedpattern. The deposit also needs to be thick enough to transfer to ametal surface while retaining its acid resistance properties.

In some implementations the viscosity is greater than 20 cps, while inothers the viscosity is below 8 cps at a temperature range of 20 to 90°C. Also, it is possible to demonstrate these viscosities at a morenarrow range of temperatures. Specifically, in specific embodiments theacid-etch resist has a viscosity greater than 20 cps at a temperature of90° C.

In specific embodiments the acid-etch resist has a viscosity greaterthan 50 cps at a temperature of 90° C., while in certain embodiments theacid-etch resist has a viscosity of greater than 70 cps at a temperatureof 90° C. In specific embodiments the acid-etch resist has a viscositygreater than 20 cps at a temperature of 20° C., in specific embodimentsthe acid-etch resist has a viscosity greater than 50 cps at atemperature of 20° C., while in certain embodiments the acid-etch resisthas a viscosity of greater than 70 cps at a temperature of 20° C. Inspecific embodiments the acid-etch resist has a viscosity greater than20 cps at a temperature of 50° C., in specific embodiments the acid-etchresist has a viscosity greater than 50 cps at a temperature of 50° C.,while in certain embodiments the acid-etch resist has a viscosity ofgreater than 70 cps at a temperature of 50° C.

In specific embodiments the acid-etch resist has a viscosity less than100 cps at a temperature of 20° C., in specific embodiments theacid-etch resist has a viscosity less than 50 cps at a temperature of20° C., while in certain embodiments the acid-etch resist has aviscosity of less than 70 cps at a temperature of 20° C. In specificembodiments the acid-etch resist has a viscosity less than 100 cps at atemperature of 50° C., in specific embodiments the acid-etch resist hasa viscosity less than 50 cps at a temperature of 50° C., while incertain embodiments the acid-etch resist has a viscosity of less than 70cps at a temperature of 50° C. It is important to select a viscositythat: allows the acid-etch resist to flow properly prior to ink jetting,allows the acid-etch resist to be adequately jetted out of the ink-jetapparatus, and still allows the acid-etch resist to form a compactdeposit onto the substrate that does not readily flow laterally so as toblur the deposited pattern. The deposit also needs to be thick enough totransfer to a metal surface while retaining its acid resistanceproperties.

It is also typically necessary to have the acid-etch resist demonstratesurface tension sufficient to retain the ink deposits substantiallywhere they are placed on the substrate, while still allowing thedistinct deposits to flow show enough flow so as to slightly merge withneighboring dots. Such properties are dictated in part by viscosity, butalso by surface tension. Generally the acid-etch resist composition canhave a surface tension of 24 to 36 dynes/cm. In some embodiments thesurface tension will be less than 24 or greater than 36 dynes/cm.Specific acid-etch resist compositions have surface tensions greaterthan 24 dynes/cm. Other specific acid-etch resist compositions havesurface tensions less than 36 dynes/cm.

Particle size of the deposited acid-etch resist will often be less than2 μm, frequently less than 1 μm. It will be understood, however, that insome embodiments the particle size will be greater than 2 μm. The vaporpressure of example printable acid-etch resists is often below 50 torr,typically below 30 torr, and optionally below 20 torr.

As noted above, the acid-etch is optionally UV curable in someimplementations. The UV source can include mercury vapor lamps, lightemitting diodes, and other UV sources. Generally it is desirable to havea UV source that permits rapid cure of the acid-etch resist, asnecessary. Also, as discussed more fully below, a two-step curingprocess offers significant benefits. In such two-step curing processesthe resist is initially cured at a low UV dosage to prevent undesirableflow of the resist, followed by a secondlater high UV dosage to morefully cure the resist. In some implementations it is also desirable todo a final cure of the acid-etch resist after the resist has beentransferred to the metal surface. Such cure steps can be more complete,because it is not necessary to subsequently transfer the resist again,and thus the resist does not need to remain tacky.

In some implementations the acid-etch resist comprises a UV curablematerial comprising a hydrocarbon resin combined with reactive diluent,often reactive monomer diluents. The reactive monomer diluents oftencontain acrylate reactive groups. Suitable hydrocarbon resins can beselected so as to offer tackifying properties to the acid-etch resist.The resins can have, for example, a T_(g) of 60 to 100° C. in someembodiments, while glass transition temperatures below 60° C. or greaterthan 100° C. are suitable in some embodiments. The reactive diluents,often monomers, frequently have a molecular weight above 100, generallyabove 150. Molecular weights below 1000 are often desirable, and evenmore typically below 500. Suitable monomers include many reactivemonomers with molecular weights from 100 to 500. It will be appreciatedthat not all monomer within the composition must be reactive or containa reactive group, but that sufficient reactive sites must be presentwithin the resin and monomer composition to provide adequate UV curingto create a transferable acid-etch resist.

An example acid-etch resist suitable for use with the present inventioncontains Norsolene S-135 hydrocarbon tackifier (available from SartomerCompany Inc. of Exton, Pa.), monofunctional monomer diluents such asSR-504 and SR-256 available as well from Sartomer Company Inc. of Exton,Pa., and a UV curing initiator, such as Irgacure 819. Furtheringredients can include small amounts of MEHQ (UV inhibitor), Irganox1076 (a monofunctional hindered phenolic antioxidant) and Orasol Blue GL(a dye). SR-256 is the trade name for 2(2-ethoxyethoxy)-ethyl acrylate,which is water dispersible, monofunctional monomer having a molecularweight of 188, a Tg of −54° C., and a viscosity of 6 cps @ 25° C. SR-504is the trade name for ethoxylated nonyl-phenol acrylate, which is a lowodor, low volatility monomer for use in UV and E-beam polymerization,having a molecular weight of 450, surface tension of 33.5 dynes/cm, anda viscosity of 100 cps @ 25° C. Norsolene S-135 is a light colored, lowodor aromatic resin that is solid at room temperature, and has asoftening point of 133° C., T_(g) of 81.7° C.

In one example embodiment, the acid-etch resist contains approximately23 parts by weight Norsolene S-135; approximately 36.5 parts by weightSR-504; and approximately 34 parts be weight SR-256; plus approximately2.8 parts by weight Irgacure 819, 0.09 parts by weight MEHQ, 0.14 partsby weight Irganoz 1076, and 2.83 parts by weight Orasol Blue GL.

Carrier Substrate

Carrier substrates used in accordance with the present invention can beof varying compositions and constructions. In general, the carriersubstrate must accept the acid-etch resist and retain it sufficientlyfor handling and positioning onto a mold without distortion, but mustthen release the acid-etch resist onto the metal mold surface afterpositioning (and optional treatment, such as with a solvent to separatethe resist from the carrier substrate). Preferably, the carriersubstrate is flexible, thin, transparent or substantially transparent,minimally stretchable, and stable under various levels of ambienthumidity.

As discussed above, the carrier substrate (onto which the acid-etchresist is deposited) can include a thin top layer along with a thickercarrier layer. The thin top layer is preferably about 5 to 15 micronsthick for ease of bending around curves on a mold surface. In someimplementations the top layer that receives the acid-etch resist will betoo thin to support itself or to support the acid-etch resist withoutdistortion. In such implementations it is particularly desirable to havea two-layer substrate: a top layer that receives the acid-etch resistplus a carrier layer to hold this top layer.

In some embodiments one or more layers of the acid-etch resist will havean adhesive bond to the carrier substrate that is readily released underspecific conditions, such as moistening the carrier substrate with wateror another solvent. In other embodiments the acid-etch resist will havea stronger bond to the carrier substrate, but will cohesively break whenthe carrier substrate is removed such that a portion of the acid-etchresist remains on the carrier substrate, but the majority of theacid-etch resist is retained on the surface of the mold. Generally it isdesirable to have the bond between the mold surface and the acid-etchresist be significantly stronger than the bond between the acid-etchresist and the carrier substrate. Also, the acid-etch resist desirablyhas a relatively high cohesive strength, so that an adhesive breakoccurs between the acid-etch resist and the carrier substrate, asopposed to a cohesive break.

The carrier substrate can include polyester; polypropylene; andcarbohydrate polymers, including cellulose, modified cellulose,cellophane, carboxymethylcellulose, hydroxypropyl cellulose, starch anddextrins, pectin, and alginates. These carbohydrate polymers can becoated as a thin water soluble or insoluble film onto a carrier film.Specifically, the substrate may be, for example, a polyester containinga coated hydrolyzed polyvinyl alcohol. Another specific suitable carriersubstrate for some applications includes, for example, 3-4 mil polyestercoated with fully hydrolyzed polyvinyl alcohol of generally less than 50microns, often from 3 to 20 microns, and preferably from about 5 to 10microns thick.

In certain embodiments the carrier substrate is penetrable and/orsoluble in water or other solvents, so as to facilitate removal of thecarrier substrate from the mold. Typically the water or solvent willhave a materially lower impact on the acid-etch resist, so as to avoidalso dissolving or excessively softening the acid-etch resist when thecarrier substrate is softened or removed.

In certain embodiments the substrate comprises a multi-layerink-receptive substrate, the ink-receptive substrate comprising amicro-porous ink receptive layer; a degradable binder layer; and acarrier layer. The degradable binder layer is positioned intermediatethe micro-porous ink receptive layer and the insoluble carrier layer. Insome embodiments the micro-porous ink receptive layer comprises aluminaparticles or other water-insoluble particles, such as silica particles.Generally the alumina particles are held in place by polyvinyl alcoholor other organic matrix.

In certain implementations a fluorescing dye is added to the substrateto permit inspection of the substrate to confirm proper transfer of anacid resist to surface to be etched. For example, the fluorescing dyemay be incorporated into the ink receptive layer, the binder layer, orboth. By incorporating the fluorescing dye into these layers, it ispossible to visually inspect the surface to be etched to confirm thatthere has been a proper printing and transfer of acid resist.

The use of the fluorescing dye is particularly useful in the inkreceptive layer for confirmation that there has been proper transfer ofthe acid resist and that the acid resist is properly developed to removeareas that have not been printed upon (thereby allowing acid etching).Generally in such implementations the areas that have not received acidresist are washed away during processing of the film (after applicationto the surface to be etched), simultaneously carrying away thefluorescing dye in those areas. After processing some dye typicallyremains in the portion of the substrate that has received the acidresist, allowing easy visual inspection to confirm acid resist positionand integrity, as well as to confirm that processing has removed excessportions of the substrate.

In certain implementations the micro-porous ink receptive layercomprises at least 1040 percent by dry weight porous alumina or silica,while in other implementations the micro-porous ink receptive layercomprises at least 50 percent by dry weight porous alumina or silica;and in other implementations the micro-porous ink receptive layercomprises at least 80 60 percent by dry weight porous alumina. In stillother implementations the micro-porous ink receptive layer comprises atleast 70 percent by dry weight porous alumina.

When polyvinyl alcohol is used in the micro-porous ink-receptive layer,the ink receptive layer typically comprises at least 10 percent by dryweight polyvinyl alcohol, and in certain embodiments the micro-porousink receptive layer comprises at least 20 percent by dry weightpolyvinyl alcohol, and optionally at least 30 percent by dry weightpolyvinyl alcohol. In some implementations the ink receptive layercomprises at least 50 percent polyvinyl alcohol, at least 70 percentpolyvinyl alcohol, or even more than 90 percent polyvinyl alcohol. In anexample formulation the micro-porous ink receptive layer comprises from60 to 80 percent by dry weight porous alumina and from 20 to 40 percentby dry weight polyvinyl alcohol.

The degradable binder layer can include, for example polyvinyl acetateand/or polyvinyl alcohol. In one such implementation the degradablebinder layer comprises at least 10 percent by dry weight polyvinylacetate and at least 50 percent by dry weight polyvinyl alcohol;optionally at least from 15 to 35 percent by dry weight polyvinylacetate and from 65 to 85 percent by dry weight polyvinyl alcohol. Thisdegradable binder layer is generally peelably removable from the carrierlayer after printing. After removal of the carrier layer, the binderlayer, ink receptive layer and acid etch resist are applied to a moldsurface (with the acid etch resist and ink receptive layer in contactwith the mold surface and the binder layer exposed). Suitable careerlayers include, for example polyester. The carrier layer is at generallyat least 1 mil thick.

One example substrate comprises a multi-layer ink receptive substrate,the ink-receptive substrate comprising an ink receptive layer comprisingat least 50 percent by weight of porous alumina; a degradable binderlayer comprising at least 25 percent by weight polyvinyl alcohol; and asubstantially water-insoluble carrier layer; wherein the degradablebinder layer is positioned intermediate the micro-porous ink receptivelayer and the insoluble carrier layer.

Configuration of a suitable carrier substrate 10 is shown in FIG. 1,which indicates an enlarged cross section of insoluble carrier layer 12(such as a polyester layer), plus a degradable binder layer 14, and amicroporous ink-receptive layer 16. The carrier substrate contains a topsurface 18 and a bottom surface 19. The top surface 18 receivesacid-etch resist from an inkjet printer, while the bottom surface 19allows for ready handling of the substrate 10. FIG. 2 shows a subsequentstep of the process of the invention, in which an acid-etch resist 20has been deposited onto the top surface 18 of the carrier substrate 10,specifically onto microporous ink-receptive layer 16. The acid-etchresist 20 is shown having somewhat distinct topical relief. In actualuse this relief, as well as the space between deposits of acid-etchresist 20 can be readily adjusted by the rate of cure of the resist, aswell as the viscosity and surface tension of the acid-etch resistcomposition 20.

After sufficient curing of the acid-etch resist 20 (if a curablecomposition is used), the carrier substrate 10 can be applied do a metalsurface. In some implementations the insoluble carrier layer 12 isremoved before the acid-etch resist 20 is applied to the 24 surface ofthe metal 22 to be etched, while in other implementations the insolublecarrier layer 12 is removed after the acid-etch resist 20 is applied tothe metal surface. However, it can be quite desirable to remove theinsoluble carrier layer 12 before the acid-etch resist 20 is applied tothe metal surface because the remaining portion of the carrier substrate10 is generally far more flexible than the insoluble carrier layer 12.Thus, removal of the insoluble carrier layer 12 allows the remainingdegradable binder layer 14 and ink-receptive layer 16 onto which theacid-etch resist 20 has been printed to be flexed to conform to a metalsurface that will be etched, such as a concave or convex mold surface.

FIG. 3 shows an acid-etch resist 20 after it has been applied to a metalobjectsurface 20. In this embodiment insoluble carrier layer 12 has beenremoved. A next step is typically to remove the binder layer 14, as wellas any exposed ink-receptive layers 16. The binder layer 14 can beisgenerally removed using an oxidizer, such as sodium metaperiodate,especially when the binder contains polyvinyl acetate and/or polyvinylalcohol. The removal of the binder layer 14 is often necessary so as toexpose underlying portions of the metal 22.

FIG. 4 shows the next step of the process, in which the acid-etch resist20 remains, but the binder layer 14 and most of the ink-receptive layer16 has been removed. In actual use portions of the ink-receptive layer16 might remain in contact with the acid-etch resist 20, especially whenthe ink-receptive layer 16 contains particles (alumina, silica, etc.) towhich the acid-etch resist has bonded. It will be appreciated that theseresidual portions of the ink-receptive layer 16 do not pose anysignificant negative issue with regard to acid etching the top surface24 of metal 22, because they are retained in locations where acid-etchresist is intended to prevent etching of the metal 22. In fact, incertain embodiments the presence of small amounts of remainingink-receptive layer 16 can provide the reducing tackiness of the exposedacid-etch resist while also providing a small additional acidresistance. FIG. 5 shows the metal 22 after etching, including etchedportions 26, along with retained acid-etch resist 20. Thereafterremaining acid-etch resist is removed, as shown in FIG. 6.

Ink Jet Printer

The ink jet printers used to print the acid-etch resist can use variousink jet printing processes, including drop on demand thermal orpiezoelectric systems. Optionally, the ink jet printer can usecontinuous printing. In thermal printing, a print cartridge with aseries of tiny electrically-heated chambers is used. The printer runs apulse of current through the heating elements. A steam explosion in thechamber forms a bubble, which propels a droplet of ink onto the paper.The ink's surface tension pumps another charge of ink into the chamberthrough a narrow channel attached to an ink reservoir. Typically thermalprinting techniques use ink that is water-based.

In the alternative, the ink jet printer may use a piezoelectric ink jetthat has one or more piezoelectric crystals in each nozzle instead of aheating element. When current is applied, the crystal bends, forcing adroplet of ink from the nozzle. Piezoelectric ink jet technology allowsa wider variety of inks than thermal or continuous ink jet printing.

Finally, a continuous ink jet method can be used. In continuous ink jettechnology, a high-pressure pump directs liquid ink from a reservoirthrough a microscopic nozzle, creating a continuous stream of inkdroplets. A piezoelectric crystal causes the stream of liquid to breakinto droplets at regular intervals. The ink droplets are subjected to anelectrostatic field created by a charging electrode as they form. Thefield is varied according to the degree of drop deflection desired. Thisresults in a controlled, variable electrostatic charge on each droplet.Charged droplets are separated by one or more uncharged “guard droplets”to minimize electrostatic repulsion between neighboring droplets. Thecharged droplets are then directed (deflected) to the receptor materialto be printed by electrostatic deflection plates, or are allowed tocontinue undeflected to a collection gutter for reuse. The more highlycharged droplets are deflected to a greater degree. One of theadvantages of continuous ink jet printing is freedom from nozzleclogging as the jet is always in use.

Methods

In one method of the invention, a first step involves generating agraphics file of a desired texture pattern. Typically such graphicsfiles are generated on a computer. This file is then output to an inkjet printer, which is configured to print using an acid-etch resist ink.The carrier transfer substrate onto which the acid-etch resist isdeposited can contain one or more layers. For example, it can contain aremovable carrier layer (such as polyester) with a release coating, orcan contain a removable carrier layer with an additional binder layerand/or ink receptive layer. Thus, in some embodiments the carriersubstrate contains an insoluble carrier layer and an ink receptive layerthat is removable from this carrier layer. The ink receptive layer maybe adhered to the insoluble carrier layer by the binder layer. In suchembodiments, after the acid-etch resist is printed onto the inkreceptive layer, the insoluble carrier layer and binder layer are peeledapart and the carrier layer discarded. The binder layer and inkreceptive layer, which has an acid-etch resist pattern printed onto it,are then applied to a metal surface to be etched. Pressure is applied tothe exposed surface of the binder layer so as to press the ink jetprinted pattern of acid-etch resist onto the metal surface to betexturized. Thereafter the binder layer can be removed, such as byoxidizing, moistening, heating or further exposing to UV radiation.Theacid-etch resist ink is printed onto a sheet of the carrier substrate.As noted above, the carrier substrate typically contains a first carrierlayer and a second carrier layer. The first carrier layer is removedfrom the printed substrate, leaving the second carrier layer along withthe ink jet printed pattern. The second carrier layer and ink jetprinted pattern are then applied to the surface to be texturized (suchas the interior of a mold). A light pressure is generally applied to theback of the second carrier layer so as to press the ink jet printedpattern of acid-etch resist ink onto the surface to be texturized.Thereafter the second carrier layer can be removed, generally by firstmoistening the second carrier layer, waiting a few minutes, and thenremoving the second carrier layer. The acid-etch resistant patternremains attached to the surface to be texturized after removal of thebinder layer, and, and thereafter the texturization process canproceedoccurs by exposing the metal surface to an acid.

It is often desirable, to perform a two-step curing of the acid-etchresist. This can be desirably accomplished, for example, by a low-powerpartial initial cure, followed by a higher power second cure. Thelow-power partial cure is designed to thicken the ink such that it doesnot readily smear or significantly flow, yet can spread slightly betweendots to create a more solid pattern. Thus the initial cure allows forvery low flow levels adequate for dots of ink-jetted acid-etch resist tofuse together slightly along their edges, but not so significantly thatthe pattern is disrupted by excessive flow.

Referring now to FIG. 7, an enlarged photo of a pattern of acid-etchresist deposited onto a carrier substrate is shown. In FIG. 7 anextremely detailed pattern of acid-etch resist has been created, havingsubstantially circular spots 40 of acid etch resist connected by thinlines 42 of acid etch resist, all separated by small triangles ofexposed substrate 44 (said exposed substrate 44 corresponding toportions of the ink-receptive layer onto which no acid-etch resist hasbeen deposited). The centers of each of the spots 40 is approximately 25microns apart in the example shown in FIG. 7. Thus, the ability tocreate acid-etch resist features of just a few microns in size ispossible using the present invention.

FIG. 8 shows a metal surface etched using an acid-etch resist patternsimilar to that shown in FIG. 7. The etched surface of FIG. 8 showssubstantially circular non-etched areas 50 joined by non-etched lines 52connect them (corresponding to the spots 40 and lines 42 of acid-etchresist of FIG. 7). The surrounding triangles of etched metal 54correspond to the areas of exposed substrate 44 of FIG. 7.

The remarkable detail shown in FIG. 7 and 8 is made possible, in part,by conducting a very rapid partial cure of the acid-etch resistimmediately after deposit onto the substrate. Printing tests show thatthe acid-etch resist spreads slightly on the carrier substrate after itis printed, which can distort the image. This can be overcome by“pinning” the acid-etch resist in place after each printing pass using aUV source. If a strong UV source is used, each pass of ink retains adomed shape after it has been fully cured. The result is printing linesbeing visible on the surface of the printed image onto the metal moldafter it has been etched. Therefore, it is typically preferable to use arelatively weak UV source for pinning the ink, such as an LED mountedadjacent to the print head of the printing unit. The initial cure islikely to have a UV dose of less than 50 mJ/cm², more likely less than25 mJ/cm², even more typically less than 5 mJ/cm² or less than 1 mJ/cm2in some applications. FIG. 9 shows a acid-etch resist applied to acarrier substrate but not “pinned” using an initial cure step. Althoughthe printed pattern should have appeared much like that of FIG. 7, ithas deteriorated remarkably such that the acid-etch resist portions 60are substantially blurred with areas of exposed substrate 64.

Similarly, the final cure is desirably from a much more intense UV lightsource, often in an inert atmosphere. Suitable final curing ofteninvolves doses of more than 100 mJ/cm², more than 200 mJ/cm², andoptionally more than 300 mJ/cm². The energy dose can be raised to allowfor better repositioning or lowered to allow for higher tack andadhesion to the metal surface to be etched. The dosesdoes should be highenough to prevent spreading of the acid-etch resist over time beforeapplication to the mold.

The use of multiple pattern transfers will require that the transfers bealigned and joined together. The transfer is then burnished onto thesurface, and with the use of a releasing agent, the tissue carrier isremoved. Match lines and fitted contours can be blended by hand using aliquid acid resistant material. After an inspection, the mold is readyto move on to the etching area. A mold may either be submersed in anacid bath or hung vertically and sprayed with acid. The type of metalalloy will determine the proper acid formula to be used. The desireddepth is governed by the temperature of the mold and acid combined withthe amount of time the mold is exposed to the acid.

EXAMPLES

Various example formulations were evaluated to determine suitability forthe present invention. The requirement for adhesion to steel wasevaluated by placing the cured acid-etch resist sample on a piece ofhighly polished P20 high carbon steel and testing release of theacid-etch resist from the steel.

The first set of samples evaluated were established ink jet inks provento work in DOD print heads. These samples included solvent based and UVcurable inks from Sunjet (SOV, UPA), and Lavalnk (Ecosolvent 640). As agroup, none of the samples tested had significant adhesion to the steelafter curing. These results can be viewed as typical because ink jetinks for conventional printing are formulated to be tack-free after curefor handling and storage purposes.

The second set of samples evaluated were liquids known to beacid-resistant. The samples included Blue 212 from Nazdar, CM-34449 forCudner & O'Conner, Sue-600B from Seoul Chemical, and NTC-W70 from CoatesChemical. None of the samples evaluated adhered to the steel sampleafter curing.

Solvent-based pressure sensitive adhesives (PSAs) were also evaluated.The samples included PS6776M1 from Clifton Adhesives, PS149 from Valpac,and 280A from Dow Coming. These PSA samples had good adhesion to metal,but had to be diluted to fall within the desired viscosity range for DODprinting (8 to 20 cps). When diluted to the proper viscosity, thesamples had a solid content of 5 to 8%. This solid content is relativelylow for most applications of the invention, and is likely to make resistbuildup difficult and could require multiple ink jet head passes overthe substrate. Also, the solvent used for dilution (toluene) has a lowsurface tension that made ejection of droplets from a DOD print headvery difficult.

The next set of samples tested was based on a UV curablepressure-sensitive adhesive formulation. The formulations consisted of ahydrocarbon tackifier (S-135), and two low viscosity, monofunctionalmonomer diluents (SR-256, SR-504), all available from Sartomer. Themonomer content was increased to reduce the viscosity (110 cps at 25°C.) and 3% of the initiator Irgacure 819 (a photo initiator for radicalpolymerization of unsaturated resins upon UV light exposure) was addedto the fluid. The ink jetability of the fluid was tested using a SM-128print head from Spectra at a temperature of 70° C. The fluid wasobserved to have good jetting properties. The fluid was then coated on asheet of 2 mil PET using a wire-wound rod at a thickness of 0.6 mils,and cured using a 5 kW metal halide exposure unit for 100 units at adistance of 23 inches. The cured film was pressed to the polished steelsample and demonstrated high adhesion. The high temperature stability ofthe fluid was also evaluated by placing a sample of the fluid, withinitiator, at 180° F. for one week. No gelling or increase in viscositywas observed in the fluid.

This initial formulation is shown below, but had a viscosity of 290 cpsat 25° C., too high for ink jetting even at elevated temperatures.Tackifier S-135 32.95 Monomer SR- 31.43 256 Monomer SR- 33.52 504Stabilizer MEHQ 0.04 Antioxidant 1076 0.1 Photoinitiator TZT 1.96 Total:100

A modified formulation was produced as follows: Tackifier S-135 24.27Monomer SR-504 37.65 Monomer SR-256 35.17 Photoinitiator 819 2.91 100.00

In a first example, in order to test this modified formulation, acarrier substrate was prepared by coating a fully hydrolyzed PVA90-50/water solution (10%) in a layer 2 mils thick on sheet of polyesterand dried at 70° C. for 15 minutes. The resulting PVA layer was 7microns thick.

In a next step, the test formulation was printed onto the PVA layerusing a Spectra SE128 print head with an Apollo II Print headcontroller. The head voltage was 75 volt, the pulse width was 8 msec andthe rise and fall was 2 msec. The head temperature was set at 70° C.Ink-jet printing was done manually onto a piece of the carriersubstrate. Thereafter, the formulation was exposed to UV using a 1 KWmedium pressure Hg-bulb at a distance of 15 cm, with an exposure of 100o1000 units.

Cured acid resist on the PVA sub layer of the carrier substrate waspressed upon P-20 highly polished steel surface and the polyesterbacking was removed. Water was sprayed over the PVA layer and left inplace for 3 minutes, after which the PVA had wrinkled and was removedleaving acid resist on the metal surface. Transferred acid resist wasexamined under a microscope and found to be minimally smeared over themetal: most of the pattern features were as they were seen on PVA layerbefore transfer.

In a second example, the same technique was used as described above, butinstead of PVA/polyester construction for the carrier substrate, asingle-layer carrier was used of 0.5 mils thick cellophane. After curingof acid resist and pressing upon P-20 steel article, water was sprayedover and let to work for 3 minutes. Removal of cellophane sheet leftacid-resist on the metal.

In a third example, acid resist fluid described in the first example wascoated on polyester using wire-rod #6. UV-curing was done exposing thefluid under nitrogen with a 5 KW medium pressure Hg-bulb at a distanceof 36 inches. Sufficient curing of acid resist in these conditions wasachieved with a dose of 100 mJ/cm².

1. A method of creating a texturized surface, the method comprising:generating a graphics file; sending the graphics file to an ink jetprinter; printing the graphics file in an acid-etch resist compositiononto a substrate material; transferring the acid-etch resist compositiononto a surface to be texturized; and etching the surface using an acid.2. The method of claim 1, wherein printing comprises using an ink-jetprinter.
 3. The method of claim 1, wherein the acid-etch resistcomposition comprises a curable composition.
 4. The method of claim 1,wherein the acid-etch resist composition comprises a UV-curablecomposition.
 5. The method of claim 4, wherein the acid-etch resistcomposition remains tacky after UV curing.
 6. The method of claim 1,wherein the acid-etch resist has a viscosity of 8 to 20 cps at 20° C.before curing.
 7. The method of claim 1, wherein the acid-etch resisthas a viscosity of 8 to 20 cps at 90° C. after curing.
 8. The method ofclaim 1, wherein the acid-etch resist is cured after printing but beforedeposit onto the surface to be texturized.
 9. The method of claim 8,wherein the acid-etch resist is cured in a two-step process, the firststep comprising curing at dose below 10 mJ/cm², and the second stepcomprises curing at a dose of greater than 50100 mJ/cm².
 10. The methodof claim 8, wherein the acid-etch resist is cured in a two-step process,the first step comprising curing at dose below 5 mJ/cm², and the secondstep comprises curing at a dose of greater than 150 mJ/cm².
 11. Anink-jetable acid-etch resist, the ink-jetable acid-etch resistcomprising: from 10 to 50 percent by weight of a tackifier; from 20 to90 percent by weight of one or more reactive monomers; and aphotoinitiator.
 12. The ink-jetable acid-etch resist of claim 11,wherein the resist comprises: from 10 to 30 percent by weight of atackifier; from 30 to 70 percent by weight of monomer; and aphotoinitiator.
 13. The ink-jetable acid-etch resist of claim 11,wherein the acid-etch resist has a viscosity of 8 to 20 cps at atemperature of 90° C.
 14. The ink-jetable acid-etch resist of claim 11,wherein the acid-etch resist has a viscosity of 8 to 20 cps at atemperature of 20° C.
 15. The ink-jetable acid-etch resist of claim 11,wherein the acid-etch resist further comprises a UV inhibitor.
 16. Amulti-layer ink receptive substrate, the ink-receptive substratecomprising: a micro-porous ink receptive layer; a degradable binderlayer; and a carrier layer; wherein the degradable binder layer ispositioned intermediate the micro-porous ink receptive layer and theinsoluble carrier layer.
 17. The multimutli-layer ink receptivesubstrate of claim 16, wherein the micro-porous ink receptive layercomprises alumina or silica particles.
 18. The multimutli-layer inkreceptive substrate of claim 16, wherein the micro-porous ink receptivelayer comprises substantially water-insoluble particles.
 19. Themulti-layer ink receptive substrate of claim 18, wherein thesubstantially water-insoluble particles comprise alumina or silicaparticles.
 20. The multimutli-layer ink receptive substrate of claim 16,wherein the micro-porous ink receptive layer includes alumina particles.21. The multimutli-layer ink receptive substrate of claim 16, whereinthe micro-porous ink receptive layer comprises polyvinyl alcohol andporous alumina particles.
 22. The multimutli-layer ink receptivesubstrate of claim 16, wherein the micro-porous ink receptive layercomprises at least 1040 percent by dry weight porous alumina.
 23. Themultimutli-layer ink receptive substrate of claim 16, wherein themicro-porous ink receptive layer comprises at least 3050 percent by dryweight porous alumina.
 24. The multimutli-layer ink receptive substrateof claim 16, wherein the micro-porous ink receptive layer comprises atleast 60 percent by dry weight porous alumina.
 25. The multimutli-layerink receptive substrate of claim 16, wherein the micro-porous inkreceptive layer comprises at least 8070 percent by dry weight porousalumina.
 26. The multimutli-layer ink receptive substrate of claim 16,wherein the micro-porous ink receptive layer comprises at least 10percent by dry weight polyvinyl alcohol.
 27. The multimutli-layer inkreceptive substrate of claim 16, wherein the micro-porous ink receptivelayer comprises at least 20 percent by dry weight polyvinyl alcohol. 28.The multimutli-layer ink receptive substrate of claim 16, wherein themicro-porous ink receptive layer comprises at least 30 percent by dryweight polyvinyl alcohol.
 29. The multimutli-layer ink receptivesubstrate of claim 16, wherein the micro-porous ink receptive layercomprises at from 60 to 80 percent by dry weight porous alumina and from20 to 40 percent by dry weight polyvinyl alcohol.
 30. The multi-layerink receptive substrate of claim 16, wherein the degradable binder layercomprises polyvinyl acetate.
 31. A multi-layer ink receptive substrate,the ink-receptive substrate comprising: an ink receptive layercomprising at least 50 percent by weight of porous alumina; a degradablebinder layer comprising at least 25 percent by weight polyvinyl alcohol;and a substantially water-insoluble carrier layer; wherein thedegradable binder layer is positioned intermediate the micro-porous inkreceptive layer and the insoluble carrier layer.
 32. The multi-layer inkreceptive substrate of claim 31, wherein the ink receptive layercomprises from 60 to 80 percent by weight of porous alumina.
 33. Themulti-layer ink receptive substrate of claim 31, wherein the inkreceptive layer comprises from 65 to 75 percent by weight of porousalumina.
 34. The multi-layer ink receptive substrate of claim 31,wherein the ink receptive layer comprises from 25 to 35 percentpolyvinyl alcohol by weight.
 35. A method of forming an acid-resistpattern, the method comprising: providing a multi-layer ink receptivesubstrate, the ink-receptive substrate comprising a micro-porous inkreceptive layer; a degradable binder layer; and a carrier layer, whereinthe degradable binder layer is positioned intermediate the micro-porousink receptive layer and the insoluble carrier layer; depositing anacid-resistant ink-jetted UVuv-curable material onto the multi-layer inkreceptive substrate; at least partially curing the acid-resistantink-jetted UVuv-curable material; and transferring the acid-resistantink-jetted UVuv-cured material to a substrate to be etched.
 36. Themethod of claim 35, wherein the step of at least partially curing theacid-resistant ink comprises a two-step curing process.
 37. The methodof claim 35, wherein the two-step curing process comprises a firstlow-powered cure followed by a second high-powered cure.